Field of the Invention
The present invention relates to a non-reciprocal circuit device and a communication apparatus using the same, and more particularly relates to a distributed constant non-reciprocal circuit device and a communication apparatus using the same.
Description of Related Art
A non-reciprocal circuit device such as an isolator and a circulator is used by being incorporated in, for example, a mobile communication apparatus such as a mobile phone and a communication apparatus used in a base station. The non-reciprocal circuit device includes a distributed constant type and a concentrated constant type. Among these types, a distributed constant non-reciprocal circuit device is suitable for an application that requires a high output such as that in a base station.
A configuration of the distributed constant non-reciprocal circuit device is described in, for example, Japanese Patent Application Laid-Open No. 2012-029123. The non-reciprocal circuit device described in Japanese Patent Application Laid-Open No. 2012-029123 has a configuration in which a central conductor having three ports extending radially with an angle of 120 degrees therebetween, and a permanent magnet that provides a magnetic field to the ferrite cores are housed in a case.
However, the non-reciprocal circuit device of a type that houses a central conductor and a permanent magnet in a case has a problem that it is difficult to realize downscaling and reduction of the manufacturing cost. Particularly, when a use in a high frequency band exceeding 20 GHz is assumed, it is required to realize considerable downscaling as compared with a non-reciprocal circuit device used in a several hundred MHz band. Therefore, it is difficult to manufacture a downscaled non-reciprocal circuit device of a type in which the central conductor and the permanent magnet are housed in a case.
Accordingly, in order to manufacture such a downscaled non-reciprocal circuit device at low cost, a multilayered non-reciprocal circuit device manufactured by using an aggregate substrate is more advantageous than the non-reciprocal circuit device housing the central conductor and the permanent magnet in a case.
FIG. 14 is a schematic perspective view showing an example of a multilayered non-reciprocal circuit device.
A non-reciprocal circuit device 100 shown in FIG. 14 includes a magnetic rotator 120 provided between two permanent magnets 111 and 112, and an external shape thereof is a substantially rectangular parallelepiped shape. The magnetic rotator 120 includes two ferrite cores 121, 122 and a central conductor 123 provided therebetween. Three ports 131 to 133 derived from the central conductor 123 are respectively connected to external terminals 141 to 143. The non-reciprocal circuit device 100 shown in FIG. 14 has a configuration in which an XY plane is a mounting surface, and the permanent magnet 111, the magnetic rotator 120, and the permanent magnet 112 are sequentially stacked in a Z direction orthogonal to the XY plane.
The non-reciprocal circuit device 100 having such a configuration can be manufactured in multiple numbers simultaneously by being stacked in a state of an aggregate substrate and then divided into plural pieces by dicing. Accordingly, the manufacturing cost can be decreased and the entire size thereof can be downscaled.
However, in the non-reciprocal circuit device 100 shown in FIG. 14, the external terminals 141 to 143 intersect the permanent magnet 111 in the Z direction. Therefore, the external terminals 141 to 143 are strongly affected by the magnetic property of the permanent magnet 111. Accordingly, inductance components of the external terminals 141 to 143 are adversely affected, thereby causing a problem that the electrical property, particularly, insertion loss deteriorates. This problem is not significant as long as a targeted frequency band is low. However, if the targeted frequency band is, for example, equal to or higher than 20 GHz, the electrical property considerably deteriorates.